There’s been a movement in the solar module industry to improve module reliability. But while solar inverter interconnection and safety standards exist, there are no well-established reliability standards. But are they really necessary? If so, in what capacity? Solar Power World reached out to industry professionals for their thoughts on the subject, and found answers differed by inverter segment and company. Here are some quick quotes to express the opinions of each.

String Inverters:“Reliability is critical in the inverter industry. If an inverter has poor quality and reliability issues, it won’t last for long in the demanding U.S. market. With the installer being liable for the first 10 years of system performance in many states, and leased systems expected to last up to 20 years, taking a gamble on companies with unproven bankability, reliability and customer service should be an unacceptable risk. There’s a need for inverters that can be field serviced in 15 minutes with one truck roll, a small service kit and no need for roof access.”—Thomas Enzendorfer, Director, Solar Energy Division, Fronius USA

“Ideally there should be inverter reliability standards considering that inverter is a critical component of a solar system. However, unlike performance data, it is very difficult to set reliability standards and more difficult to measure because the reliability data should be gathered in the field over a long period of time.”—Susanna Huang, Ginlong Technologies

“It is very difficult to standardize reliability for inverters because there is not the same set of standards around test conditions. Inverters are far more differentiated than modules, and the variation in rating and application for critical variables like temperature, power factor, DC voltage range and AC voltage, as well as grid quality, can significantly affect the reliability of an inverter. That said, it is critical that there is more transparency and standardization of inverter reliability data, because as the industry matures, developers need to access new forms of financing that require more standardization.”—Tucker Ruberti, Director of strategic marketing, Advanced Energy

-SolarMax

“Inverter manufacturers go to great time and cost lengths to be compliant with stringent UL certifications. Beyond that, companies offer long warranties, namely 10 years for string inverters. They need to be reliable or the costs will be high for the manufacturer. Companies that have products that are not built to last will not survive. The customer should factor quality into the purchase decision and not just a low price per watt, which sometime can be the driving factor without concern for three, five or 20 years down the road.”—Alan Beale, General Manager, SolarMax USA

“During the product design cycle, engineers use design guidelines at the component level to avoid component overstress, and accelerated life cycle testing to validate the robustness of the product. In production, test failures are analyzed to identify the source of failures and countermeasures are implemented. Field returns are also analyzed to identify failure modes and tracked to identify trends.”—Chavonne Yee, Director of product management at Power-One, a member of the ABB Group

“A blanket standard is not needed, but proving high reliability is a great weapon for competitive advantage. There are many ways to increase reliability confidence in the design process, but we have found that actual field and lab toughness testing is most effective.”—Ed Heacox, Chint Power Systems

Central Inverters:“International standards are very useful in order to unify different criteria that may apply in all countries. For this reason, we believe that it would be very helpful to develop these kinds of standards.”—Juan Luis Agorreta, Ingeteam R&D Department, Solar PV Division

“We strongly support the establishment of a reliability test standard for PV Inverter and BOS. An established standard would bring maturity to the industry, create a level playing field and allow customers to compare and differentiate between robust products from established suppliers and products with unsubstantiated claims.”—Suhas Deshpande, Director of quality and customer support at Schneider Electric Solar Business

“Reliability is designed into our inverters from the start by eliminating components that are prone to failure, and by using conservative design margins. As part of our internal testing, we also perform various reliability tests, including thermal cycling and HALT testing.”—Mark Goodreau, Solectria Renewables

-Ingeteam

“Inverter manufacturers have their own set of perspectives on reliability, and establishing standards is always a challenge. TMEIC has incorporated reliability standards from IEC for reliability cycling tests and has also established standard factory testing from field experience.”—Ryuta Ray Saka, TMEIC

“Reliability can be measured by mean time before failure (MTBF), but more importantly, there is the question of mean time to repair (MTTR). While a component failure is a relatively rare event, if it takes hours or days of downtime to repair, productivity will suffer. Therefore it is advantageous to use a design with as much modularity as possible, allowing repairs to be done rapidly and efficiently.”—Lou Lambruschi, marketing services and E-business manager at Parker Hannifin

“Solar Inverters are solid-state power electronic devices. Therefore, there is no need for a specific reliability standard as power electronic industry standards should be adhered to.”—Peter Gerhardinger, VP of Technical Sales, Nextronex

Module-Level Power Electronics:“It is common practice in telecommunication and military power equipment to meet certain predictions on product life and reliability, better known as mean time before failure (MTBF) estimates. Some form of MTBF could separate the good from the bad and force solar module manufactures to address failures with analysis and constant product improvement.”—Michael Ludgate, VP of Business Development, APS America

“Inverter reliability is as important as module reliability, mainly because the inverter is the operating system for the entire array that performs 100% of all conversion work. While module issues do affect performance, high microinverter quality will keep entire systems producing even with module reliability issues. The distributed nature of microinverters is a huge leap forward in system reliability.”—Raghu Belur, co-founder, Enphase Energy

“While standards generally govern safety, reliability can be viewed as a competitive differentiator. In an open market, quality can be a quantitative reason for choosing one supplier over another. While we certainly don’t want the market to be subjected to cheap components and low-quality suppliers because that can damage consumer adoption. We believe companies that invest in a quality product will be rewarded by the marketplace in the long term.”—Brad Dore, Director of marketing, SMA America

-SolarEdge

“Module reliability is an important aspect in the industry, specifically if it can be translated to bankability, lower cost of capital etc. Tigo Energy believes that using information technology and connecting modules into the internet of things (IOT) will enable the industry to translate material quality, module construction and field behavior into the more valuable, predictable long-term performance of the asset. This will lower the industry’s risk level, increase the availability of lower-cost funding and improve market adoption.”— James Bickford, Tigo Energy

“Since about 2 out of every 3 installations in the U.S. residential market are now built with module level electronics, it’s overdue to evaluate how we test them. Our philosophy is that components that go near or on the modules should be tested with a similar methodology as modules. That means that module-level electronics need to be tested for thermal cycle, damp heat and humidity freeze. They also need electrical component testing that solar modules don’t require, such as burn-in tests.”—Michael Rogerson,North Americamarketing manager, SolarEdge

“We believe that the entire PV market needs a dedicated focus on reliability, and that includes inverters and power electronics of all kinds. Most string and central inverters have, at best, a 10-year design life, and most of the leases and PPAs out there are less than five years old. The industry may begin to see significant unplanned O&M expenses related to inverters that will erode returns from financed systems, unless tough, new reliability standards are adopted. Additionally, as module-level power electronics continue to grow in market share, manufacturers of power electronics must offer the same life-long warranties as module manufacturers (typically 25 years), or they will not be able to participate in this growing market. As the industry begins to expect 25-year life spans from their power electronics, that is going to put pressure on the traditional inverter manufacturers to improve their reliability.”—Craig Lawrence, SolarBridge Technologies

About The Author

Michelle DiFrangia

Comments

The reliability of solar inverters is, needless to say, very important to reach expected up-time and energy production. There is however no need for solar specific reliability standards which would only add cost to the product and ultimately to the produced energy. The core of a solar inverter and the part that really could influence the overall reliability is a power module. The power module is half of what has already been used in power converters and industrial drives for a very long time. In some processing lines and industrial applications, e.g. paper mills and rolling mills, numerous drives are set to operate with very fast ramp times and in concert with each other. With this, the reliability requirement is much higher than it will ever be in solar.